1. Field of the Invention
The present invention relates generally to oxygen systems and, more particularly, to a method and apparatus for monitoring the partial pressure of oxygen in such oxygen systems.
2. Description of the Related Art
Users of oxygen masks and air masks in general are at risk of oxygen deprivation, or hypoxia, in the event of a malfunction or breakdown in the oxygen system. High-performance military aircrafts, for example, are typically pressurized according to a schedule that often results in cabin pressure altitudes above 10,000 feet. The pilots of these aircraft are required to wear oxygen masks in order to maintain a sufficient level of oxygen. However, a malfunction of the oxygen regulating system, poor fitting of the oxygen mask, or failure of the oxygen hose or distribution system can result in hypoxia. Accordingly, a number of warning devices have been developed to detect and alert the users of air masks to hypoxia inducing conditions.
Existing hypoxia warning devices, however, are typically integrated with, or are an extension of, the oxygen systems being monitored. For example, presently available hypoxia warning devices commonly share the same power source as the oxygen systems. As a result, a malfunction or breakdown in the oxygen system can often result in misleading or even false indications of the oxygen partial pressure.
In addition, existing hypoxia warning systems typically only analyze the air that is being supplied to the mask as opposed to analyzing the air directly within the mask. These systems often fail to detect loose or poor fitting oxygen masks or hose connections from the oxygen system to the mask. As a result, hypoxic conditions can and do frequently arise even though the oxygen level of the air that is being supplied is normal. Also, a failure in the aircraft pressurization system which causes the cabin pressure to slowly decrease can result in hypoxic conditions with no observed failure in the oxygen supply system.
Moreover, current hypoxia warning devices typically warn the users of a potentially hypoxic condition by sounding an alarm, illuminating a visual indicator, or a combination of both. These warning indicators, however, may not be adequate or effective when the user has already begun to experience some of the symptoms of hypoxia. For example, a warning tone or light may more easily go unnoticed or unheeded by a pilot who is already groggy, drowsy, or who has a reaction time that is slowed by the onset of hypoxia. Also, warning systems that tie into an aircraft's existing caution lights and audible tones require significant and costly modifications to every aircraft that the system is applied too.
Accordingly, it is desirable to be able to provide an improved hypoxia warning device that is independent of the oxygen system being monitored, monitors the air directly within the air mask, requires minimal or no modifications to existing airplane cockpits or emergency cabin depressurization systems, and is also sufficiently annoying, irritating, and aggravating to provoke the user into taking prompt and immediate corrective actions.